It could be...Tiergan!
First, think about it- Oralie and him don't talk, they have no connection. Secondly, read chapter 34 of the first book. Just do it. Proof is right there. Thirdly, he literally hates the council yet he came back to them just to mentor a random child(ok, maybe not random, and yes he half did it for Prentice). He cares about Sophie sooooooo much.
This one is far fetched, but I feel if Forkle had a secret twin brother, anything is possible. Glimmer could be....Cyrah endal. Think about it- She was mad and heartbroken because of Prentice's mind break- especially at the council and the black swan for letting that happen to him. She decides to form an alliance with a rising rebel group who hates the black swan and the council. She fakes her death- yes, wylie saw her fading, but SHE'S A FLASHER SHE CAN MANIPULATE LIGHT. Glimmer is also a flasher.
Also- to y'all saying Jolie is Glimmer- Why in the world would she help the neverseen???
3. Lady Gisela has another ability
This one is a maybe, I mean she's a polygot.
4. Jensi's brother is blur, cuz they're both phasers, but this one is pretty obvious.
5. Iggy is a secret FBI spy and is part of the neverseen and that's how they keep tabs on sophie....i'm just kidding don't worry lol
Put more theories in the comments!! I want to see!!!